The term web is used to describe materials which are manufactured and processed in a continuous, flexible strip form. Web materials cover a broad spectrum from extremely thin plastics to paper, textiles, metals, and composites. Web handling refers to the physical processes related to the transport and control of web materials through processing machinery. Web handling systems facilitate transport of the web while it is being processed in processing machinery, which is typically an operation specific to the particular web product. For example, in the case of webs used for consumer products, the web is coated, printed, or laminated. A typical operation involves transporting a web in rolled, unfinished form from an unwind roll to a rewind roll through processing machinery where the required processing operations are performed. The web is transported by rollers driven by motors in a process line. The quality of the finished web depends on how it is handled on the rollers during transport. Lateral and longitudinal motion of the web, and web tension, are controlled during transport.
Accurate web guiding is becoming increasingly demanding due to variation in web materials, both in the gauge and opacity of the materials, being processed in a single process line. Since web lateral position is used as feedback for controlling a web guide, accurate web edge detection becomes increasingly important for proper guiding of the web. Web lateral position is defined generally to mean the position of the center and edges of the web relative to a fixed position on the axis of rotation of the roller along the axis of rotation of the roller. This axis of rotation of the roller is generally perpendicular to the direction of travel of the web.
What is needed is a system and method for addressing the above, and related, issues.